Certain integrated circuits, particularly high density dynamic random access memory devices, are sensitive to alpha particle radiation. In such devices, the necessarily small size of the storage capacitors in each cell allows the data stored therein to be destroyed if struck by an alpha particle.
Alpha particles travel relatively slowly, and are stopped rather easily, so an integrated circuit within a package, which may be plastic or ceramic or another material, generally is unaffected by alpha particles in the ambient. The package material itself, however, is a substantial source of such particles, particularly if the package is of ceramic. Ceramic packages are usually Alumina of high purity. Even high purity Alumina, however, contains a certain amount of thorium and uranium which are emitters of alpha particles.
Before a material can be accepted as a memory packaging material, the material must be characterized with respect to its alpha particle emissions to determine whether the radiation is sufficiently low to provide an acceptable package. Presently, materials are tested in several ways: a large number of memory devices are packaged with the material and placed on operating test to determine the average soft-failure rate, or gas proportional detectors are used to monitor the material before molding. The number of required parts and the complexity of the test make the operating test method undesirable, and leaves open the possibility of confusing other soft-error types with alpha particle hits. The gas proportional test method does not accurately reflect the environment in which the device will operate.
It is an object of this invention to provide a new test method and procedure for characterizing integrated circuit packaging materials.
It is a further object of the invention to provide a method of packaging integrated circuits in a material characterized by the method.
It is a still further object of the invention to provide an integrated circuit packaged in the material.